Australian Tonya Lee has told a court that Rolf Harris invited her to sit on his knee in a London pub, then he sexually abused her, when she was 15 years old.

Lee, 43, gave evidence seated behind a curtain, but had waived her right to anonymity, prosecutor Sasha Wass, QC, said.

She is the fourth woman to take the stand as a complainant in Rolf Harris’s sexual assault trial, and was expected to face a grilling from his lawyers over her decision to sell her story to the Australian media last year.

Harris, 84, has pleaded not guilty to 12 charges of indecent assault against four complainants.

The last three of the charges relate to Ms Lee.

Lee was interested in theatre as an 11- or 12-year-old and joined the Shopfront Theatre youth group in Sydney, she told the court.

Just after she turned 15 she was chosen to join their six-week tour to the UK in 1986. It was a dream come true, she said, her first trip overseas.

The 14-strong group performed in cities such as Liverpool and Birmingham, and saw the sights in Scotland and Stratford-upon-Avon.

When they arrived from Sydney a surprise had been arranged – Harris was at the airport to meet the group, with his wife – he was friends with the theatre’s director.

Later Harris met the group in a pub for dinner. The group were in high spirits and sang songs. Lee sang a solo.

Then Harris said “you have a lovely voice, come and tell me a bit about yourself … come and sit down on my lap”.

She did so. He asked about her singing ambitions, and plans for the tour.

But then she noticed “he was moving back and forth, rubbing [his crotch] against me”, she said. He then started to pat her on the thigh, then moved his hand between her legs, “higher and higher”.

She was feeling very uncomfortable and “started to panic” wondering how she could get out of the situation, but Harris was still joking and laughing.

When his hand touched her intimately she made an excuse and went to the bathroom. She sat there with a “whole lot of confusion” in her head – “I really didn’t know how to handle it,” she said. She decided not to tell anyone.

Then shortly afterwards when she came out of the lavatory, Harris was waiting for her in a hallway outside the bathroom. He gave her a hug and then assaulted her again.

Harris put his hand down her top and fondled her breast, cornering her against the wall with his body, she said.

"I was petrified ... I probably should have screamed but I think I was in shock," she said.

Harris then put his hand down the top of her skirt and into her tights and underwear and put his fingers inside her.

She felt claustrophobic and trapped, she said.

"I wanted to burst into tears and I just wanted to run," she said.

Harris then gave her another hug and walked away, Lee said.

In 2013 Lee sold her story through publicity agent Max Markson for $60,000 to Woman’s Day and A Current Affair, Wass said in her opening statement to the jury two weeks ago.

“Just because she has received money, does that mean that what happened to her was not true?” Wass asked the jury. “That is what Mr Harris will suggest.”

She said Harris had already told police that he had no recollection of her and denied the allegations. “She may well be motivated by a desire for fame and financial reward,” Harris said when interviewed by detectives.

Wass said Lee had been talked into selling her story by her partner at the time.

“You may well think it is unattractive to sell your story to the newspapers and television,” she said. “But does the fact that you have done so mean that the story is untrue?”

Lee said the attack triggered bulimia, depression and a drinking problem, and coming to give evidence at the trial would lead her to be severely criticised for making money out of her experiences, Wass said.

This is the second and final week of evidence from prosecution witnesses.